Studies on the browning of potato tubers by gamma radiation, 3

The relation between the browning of potato tubers caused by gamma radiation and cultural localities or the time of irradiation after harvest was investigated, and the change of tyrosine content in irradiated potato tubers was determined. Irish Cobbler potato tubers harvested at seven localities (Kyushu, Shikoku, Kinki, Chubu, Kanto, Tohoku, Hokkaido) were irradiated with doses of 10 and 20 krad 2, 5 and 10 weeks after harvest and the observation of browning was made on the 7th day after irradiation respectively.When the tubers were irradiated 2 weeks after harvest, the browning showed marked difference among localities. In the tubers harvested in Kinki, Shikoku and Kyushu, more browning was observed in comparison with those of other localities. The tubers harvested in Kanto showed hardly browning. When the tubers were irradiated 5 weeks after harvest, the browning was reduced except for the tubers in Kyushu. In the tubers irradiated 10 weeks after harvest when the tubers egan to sprout, little browning was observed. It is suggested that the suitable time of irradiation after harvest is about 1.5-2 months after harvest.The tyrosine content varied among localities, and the content was increased by irradiation. The increasing rate of the content was greater in irradiated and browned tubers than in irradiated but non-browned tubers.